Looking for a suitable plugin!!! (2 posts)

I have a question. On my website I have 3 different categories, in which I post different articles daily. Let suppose, the Reader wants to subscribe for category 3 and wants to get the post only from category 3 and not for 2 and 1 how can I do that?

I have goggled but unfortunately I couldn't find the answer, therefore I have decided to ask the WordPress experts. May be you have a idea, how I can do it!